This invention relates to a deployable phased array antenna for a space based radar. The antenna is intended for deployment from a space shuttle which imposes volume limitations on the antenna, and therefore requires a configuration which can be folded and compressed into a relatively small compartment.
The antenna array for which this invention is provided is designed to have deployed dimensions of 86 feet by 149 feet, but when folded, it measures 8.5'.times.9.4'.times.27'. When folded, it fits conveniently into the 15'.times.30' payload volume of the space shuttles presently flown by the National Aeronautics and Space Administration.
In order to provide an array of such large dimensions, and yet be stowable in the relative small compartment of a space shutttle, this invention provides a plurality of antenna sub-arrays which permits the folding and storage of the antenna array, and the convenient deployment thereof.
In order to provide an antenna having the foregoing dimensions, it is necessary to use antenna elements that can be appropriately packaged. The tapered notch antenna, also known as a "Vivaldi" element, is disclosed in the copending application of Schnetzer, Ser. No. 07/644,176 now abandoned in favor of continuation application Ser No. 07/906,017 filed 26 Jun. 1992, entitled TAPERED NOTCH ANTENNA USING COPLANAR WAVEGUIDE. Schnetzer's Vivaldi tapered notch antenna was found to have many advantages in a folded, space based, phased array. First, since the Schnetzer antenna element uses no ground plane, the need for a continuous panel or membrane the size of the deployed antenna array is eliminated. Moreover, the antenna elements are printed on very thin dielectric substrates of Kapton, but sufficient stiffness is provided by the conductive metal remaining on the substrate.
In accordance with this invention, the antenna array is constructed in sub-arrays which are supported in a stacked and folded (stowed) condition, and then deployed by first unfolding and then expanding the stack. The sub-arrays are compressed together to yield a very compact stowed configuration, due to the absence of a continuous ground planes. The packed sub-arrays are contained within a cage like frame for launch restraint. This cage supports the RF feed network which feeds sixteen units of each sub-array. The feed network is made up of rigid suspended substrate suctions with flexible coaxial cable sections at the array hinge lines.